This invention relates to an input data sign determining method in an NC machining data creation method. More particularly, in a method of creating NC machining data by entering a tool travelling direction for each block of a part profile through use of profile symbol keys to specify the part profile, followed by entering dimensional values for each block of the part profile and using these data to create the NC machining data, the invention relates to an incremental quantity sign determining method through which the signs of incremental quantities can be determined when dimensions are specified in the form of incremental quantities along respective axes just as written on a drawing.
Automatic programming systems for lathes have come into practical use and are used to create NC tapes from a design drawing through a simple operation by entering data in a conversational mode using a graphic display screen. With such an automatic programming system, a part profile (exclusive of dimensions) can be entered merely by pressing profile symbol keys, which are located on an operator's panel, corresponding to a workpiece profile written on a design drawing. Further, according to the automatic programming system, referential information is graphically displayed on the screen from time to time and inquiries are made in ordinary language, so that dimensions and various data can be entered in response to the inquiries. When all data necessary for creation of an NC tape have been entered, the system immediately displays the blank profile and the finished profile, begins automatic calculation of NC command data and graphically displays a tool path to create an NC tape. A programming method performed by such an automatic programming system will now be described in detail. The method comprises the following steps:
(1) drawing mode selection step; PA1 (2) blank profile and blank dimensions input step; PA1 (3) part profile and part profile dimensions input step; PA1 (4) machine reference point and turret position input step; PA1 (5) process selection step; PA1 (6) tool selection step; PA1 (7) machining area and cutting conditions designation step; and PA1 (8) tool path calculation step. PA1 X=100 PA1 Z=80 PA1 X=-20, Z=35 PA1 Z=35 PA1 X=-30 PA1 Z=60 PA1 X=-25 PA1 Z=-105 PA1 X=-25
The necessary data are entered successively to eventually create the NC tape. In the third step for entering part profile and dimensions, coordinate axes and the blank profile, as well as a part profile inquiry, are displayed on the screen, one responds to the inquiry, while observing the design drawing, by pressing a profile symbol key on the keyboard in accordance with the profile on the design drawing, thus to enter the part profile (exclusive of dimensions). Following the entry of the part profile, the display screen makes an inquiry requesting the necessary dimensions, and dimensions taken from the design drawing are entered from the keyboard in response to the inquiry, thereby completing the entry of a part profile and dimensions. As an example, if the part profile has the shape shown in FIG. 1, then, in entering the part profile, predetermined profile symbol keys (keys indicated by the symbols .uparw., , .fwdarw., , , .rarw., , , ), shown in FIG. 2 and provided on a keyboard 104, are pressed in accordance with the direction of the profile in each of blocks b.sub.1 through b.sub.8. Specifically, straight line elements L.sub.1, L.sub.3 and L.sub.5 in first, third and fifth blocks b.sub.1, b.sub.3 and b.sub.5 are directed horizontally (Z axis) rightward, a straight line element L.sub.2 in a second block b.sub.2 is directed downardly toward the right, straight line elements L.sub.2, L.sub.4, L.sub.6 and L.sub.8 in fourth, sixth and eighth blocks b.sub.4, b.sub.6 and b.sub.8 are directed vertically (X axis) downward, and a straight line element L.sub.7 in a seventh block b.sub.7 is directed horizontally leftward. Therefore, entry of the part profile will be completed if the symbolic keys are pressed in the order .fwdarw., , .fwdarw., .dwnarw., .fwdarw., .dwnarw., .rarw., .dwnarw.. It should be noted that the profile symbol keys become effective as numerical value input keys automatically in dependence upon the automatic programming process steps, and it becomes possible to enter the letter of the alphabet shown at the lower right of the key tops when a shift key is pressed. Next, dimensions in each of the blocks (b.sub.1 -b.sub.8) are entered from the drawings in response to inquiries. Specifically,
is entered in response to an inquiry regarding a starting point,
in response to an inquiry regarding the first block,
in response to an inquiry regarding the second block,
in response to an inquiry regarding the third block,
in response to an inquiry regarding the fourth block,
in response to an inquiry regarding the fifth block,
in response to an inquiry regarding the sixth block,
in response to an inquiry regarding the seventh block, and
in response to an inquiry regarding the eighth block, wherein a numerical value following the letter of the alphabet X indicates an incremental quantity along the X axis, and a numerical value following the letter of the alphabet Z indicates an incremental quantity along the Z axis. The operation for entering the part profile and dimensions in the above-described third step is completed by the foregoing procedure.
When the incremental quantities of the respective blocks are entered in accordance with the above-described conventional method of creating NC machining data, the input values along the respective axes are provided with a positive or negative (+ or -) sign depending upon the coordinate values of the tool destination in each block, thus to indicate the positional relation of the destination. However, the design drawing on which the programming is based usually gives only the dimensional values of the profile, so that the programmer must himself calculate whether an input value is positive or negative when entering the incremental quantities. This makes programming a troublesome operation and is a cause of programming errors.